Ozone is generated for use in many chemical processes requiring reactions to be carried out in the presence of a strong oxidant. Ozone is also generated as an undesired by-product in other processes, e.g. during use of certain electronic equipment such as electronic photocopying machines. Because of the toxic and irritating effects on humans, any ozone present in the process waste effluents must be destroyed before said effluents can be released to the environment. The removal of ozone from the exhaust streams of the aforementioned processes to acceptable levels are not too difficult and can be achieved e.g. by thermal destruction, by adsorption employing activated carbon, or by catalytic destruction using e.g. activated carbon-supported silver or copper catalyst.
The efficient control of ozone in the environment is, however, a problem in certain situations, where space and/or energy limitations preclude the use of the aforementioned conventional ozone destruction methods. Specifically, in order to conserve fuel on long distance flights, modern aircraft fly at such high altitudes, that they often penetrate the ozone layer of the earth's atmosphere. Ozone is thereby introduced with the pressurized air into the cabin, causing discomfort and potential health hazards to passengers and flight crew. The pressurized fresh cabin air, which is provided from an intermediate compression stage in the ramjet engines, is introduced at very high rates, typically in the order of 5 pounds of air per second in larger commercial passenger planes. The use of activated carbon as an adsorbent or catalyst support for purification of the air is not a desirable solution, since the weight (approximately 400 lbs) and, more importantly, the space requirements of the purification medium to treat such large quantities of air would be excessive, and would necessitate major changes in the design of the air circulation system. Another disadvantage of activated carbon is its relatively short service life at the delivery temperatures of the compressed air (typically between 300.degree. and 400.degree. F.). Furthermore, activated carbon is quite brittle and is prone to disintegration during periods of high turbulence. Dust produced in such situations would be entrained in the purified air being supplied to the cabin and would require additional equipment for removal.
The use of higher temperatures, e.g. by taking the air from a rear stage of the engine, to destroy the ozone is technically feasible, but is energy consuming, thus significantly negating the fuel savings achieved by flying at the higher altitudes.
It is therefore an object of the present invention to provide a novel efficient catalyst composition for the reduction of ozone levels.
It is another object of the invention to provide a catalyst and a device for the destruction of unwanted ozone with minimum energy requirements which is lightweight and operates with minimum pressure drop and at lower temperatures.
It is a further object to provide an ozone control device which can be installed in the pneumatic duct of an airplane.
Further objects of the invention will become apparent from a reading of the specification and appended claims.